1. Field of Invention
The invention relates generally to micro-electro-mechanical systems (MEMS) and or micro-opto-electro-mechanical systems (MOEMS), and more specifically to apparatuses and methods used to create a MEMS or MOEMS device that utilizes a zero stiffness or near zero stiffness elastic structure.
2. Art Background
Many devices made using MEMS and MOEMS routinely require elements to provide various functionalities, such as stiffness. MEMS and MOEMS elements that provide stiffness have traditionally been obtained from a device that has a positive spring constant or stiffness. Stiffness elements such as; straight beam suspensions, tether wires, meander springs, etc. are used to suspend elements used in MEMS and MOEMS devices. Such stiffness elements are characterized by positive stiffness. Designing elements for MEMS and MOEMS devices using only positive stiffness elements is limiting. All of this can present problems.
Capacitive MEMS switches are designed with a cantilever elastic element that is deflected when a voltage is applied. The large positive stiffness of such devices is required to overcome stiction from the physical stops once the actuation voltage is removed, and to ensure that no amount of signal noise could keep the switch closed. Actuation voltages on the order of tens of volts is often required, such levels place power demands on the power supply. This can present a problem.
Ohmic MEMS switches also rely on an elastic cantilever element in their design. Ohmic contacts tend to have an increase in stiction over the cycle lifetime of the switch due to plastic deformation of the contact surfaces. In order to develop a switch with a reasonable lifetime, a sufficiently high restoring force must be part of the design. The cantilever that the micro contact is mounted on must have an even greater stiffness than the capacitive MEMS switch, thus requiring an even larger actuation voltage. This can present a problem.